Various classes of block diagrams describe computations that can be performed on application specific computational hardware, such as a computer, microcontroller, FPGA, and custom hardware. Classes of such block diagrams include time-based block diagrams such as those found within Simulink.® from the MathWorks, Inc. Natick Mass., state-based and flow diagrams such as those found within Stateflow.® from the MathWorks, Inc. Natick, Mass., and data-flow diagrams. A common characteristic among these various forms of block diagrams is that they define semantics on how to execute the diagram.